The present invention relates to an electromagnetic friction connecting apparatus such as an electromagnetic brake, an electromagnetic clutch and the like. It more particularly relates to the wiring structure for the exciting coil of an electromagnetic friction connecting apparatus, which is fixed in the housing of the driving force distribution unit of a vehicle.
As a conventional electromagnetic clutch belonging to an electromagnetic friction connecting apparatus, an apparatus which engages a multiple dish clutch mechanism by actuating an armature element with the magnetic force generated by an exciting coil which is supplied with electricity has been known, which is disclosed in Japan Laid-Open Patent Publication 2001-116063. This electromagnetic clutch includes a ring-like core element, an exciting coil installed in the concave which is formed circumferentially on the core element and has an opening in an axial direction and the ring-like armature element which is so situated that it may cover the exciting coil. This electromagnetic clutch, which is utilized for a power distribution unit that is capable of distributing the engine driving power for the right and left wheels of a vehicle, is contained in the housing of the power distribution unit. Holes for guiding harness are made on the concave bottom of the core element and also holes for installing connectors are made on the housing, since the electricity for the exciting coil of the electromagnetic clutch is supplied externally through harnesses and connectors.
The structure described above has required that the exciting coil should be installed in the concave of the core element after connecting one end of the harness to the exciting coil and guiding the other end through the hole made on the core element, when the exciting coil of the electromagnetic clutch is installed in the concave of the core element. When the electromagnetic clutch is installed in the housing, the following steps have been requested: guiding the harness coming out of the hole of the core element through the housing hole, installing the core element in the housing, connecting the harness coming out of the housing hole to the connector and mounting this connector to the housing hole.
The electromagnetic clutch, which is disclosed in Japanese Laid-Open Patent Publication 2001-116813, has a search coil which detects the magnetic flux generated by the exciting coil. Another harness thus is required for transmitting the current of electromagnetic induction by this search coil, and thereby it is necessary to prepare a hole similar to that described above in an appropriate spot and install the search coil after guiding the harness through the hole.
The object of the present invention is to provide an electromagnetic friction connecting apparatus, which allows the easier operations associated with the installation of the exciting coil or the search coil in the core element.
The present invention to assess the problems according to claim 1 provides an electromagnetic friction connecting apparatus comprising; a core element which is formed into a ring shape with a U-shaped section and secured within a housing; at least one of an exciting coil and a search coil having ring-like shapes, which is situated within a concave of the U-shaped cross section of the core element; an armature element having a ring-like shape, which is disposed opposite to an opening side of the concave of the U-shaped cross section of the core element; a pressing element which is actuated by the armature element; and a multiple dish clutch mechanism on which the pressing element exerts connecting force, wherein a plurality of wiring terminals, each of the wiring terminals including a first extension, which extends in a direction of the armature element to press the pressing element, and a second extension, which extends outward radially from an end of the first extension, are provided in at least one of the exciting coil and the search coil, wherein an end of the second extension of the wiring terminal is situated radially inside a peripheral surface of the exciting coil, wherein a plurality of connection openings, each of which allows the end of the second extension of the wiring terminal of at least one of the exciting coil and the search coil to be exposed to an outside of the housing, are formed on the core element and the housing, and wherein a plurality of couplers, each of which has an electrical sending and receiving portion, are inserted into the openings to couple to the end of the second extension of the wiring terminal. xe2x80x9cA radial directionxe2x80x9d is defined here as a direction of radius such as that of a ring-like core element or an exciting coil. xe2x80x9cSending and receiving of electricityxe2x80x9d means that an exciting coil, for example, receives electricity from an external power source, on the other hand a search coil sends the current induced by the magnetic force of the exciting coil. xe2x80x9cAn electromagnetic friction connecting apparatusxe2x80x9d includes an apparatus which is capable of engaging a clutch mechanism by the electromagnetic force exerted by an electromagnetic clutch or an electromagnetic brake.
The invention according to claim 1 allows each of the wiring terminals of the exciting coil to be housed in the connection opening formed on the core element, when the exciting coil is installed in the concave of a U-shaped cross section of the core element. The end of the second extension of each wiring terminal will not interfere with the core element in which the exciting coil is installed, since it is situated radially inside the peripheral surface of the exciting coil. If the core element is secured in the housing aligning the connection openings of the core element with those of the housing, the end of the second extension of each wiring terminal faces the outside of the housing. The coupler is inserted into the connection opening so that it may be connected to the end of the second extension of each wiring terminal.
The invention according to claim 2 provides an electromagnetic friction connecting apparatus of claim 1 wherein the search coil is disposed so that a peripheral surface of the search coil is situated radially inside the first extension of the wiring terminal of the exciting coil, and the openings of the exciting coil and the search coil which are made on the core element and the housing are offset circumferentially.
xe2x80x9cA circumferential directionxe2x80x9d is defined as a direction of the circumference such as that of a ring-like core element or a ring-like exciting coil.
The invention according to claim 2 allows each of the wiring terminals of the search coil to be housed in the connection opening for the search coil formed on the core element in addition to the effects of claim 1, when the search coil is installed in the concave of a U-shaped section of the core element. Next the exciting coil is installed in the concave of a U-shaped cross section of the core element. Each of the first extensions of the exciting coil will not interfere with the search coil since the outer peripheral surface of the search coil is situated radially inside each first extension of the wiring terminal of the exciting coil. The wiring terminals of the exciting coil and the search coil are free of interference since the connection openings for them are placed offset each other circumferentially. The search coil can thus be situated near the exciting coil.
The invention according to claim 3 or 4 provides an electromagnetic friction connecting apparatus of claim 1 or 2 respectively, wherein the housing is filled with a lubricant partially at least, seal elements of leak protection for the lubricant are provided for each of the couplers, and at least one of the connection openings for the exciting coil and the search coil is made in an upper half of the housing.
The invention according to claim 3 or 4 allows the couplers having seal elements to be inserted into the connection holes of the exciting coil and the search coil from above the housing, in addition to the effects achieved by claim 1 or 2.
The invention according to claim 5, 6, 7 or 8 provides an electromagnetic friction connecting apparatus of claim 1, 2, 3 or 4 respectively, wherein a peripheral portion of the armature element is so configured that a diameter of the peripheral portion is larger than an outer diameter of the core element, wherein the pressing element is formed cylindrically and one end of the pressing element is secured to the peripheral portion and the other end is coupled to a pressing plate of the clutch mechanism, wherein the pressing element is mated around the core element displaceably in a pressing direction, wherein the core element includes flanges located at a periphery thereof for fixing the core element to the housing, wherein a first plurality of cutouts for avoiding the flanges and a second plurality of cutouts for avoiding the couplers for at least one of the exciting coil and the search coil are provided on the pressing element, and wherein all the cutouts are positioned evenly in a circumferential direction.
The invention according to claim 5, 6, 7 or 8 provides a well-balanced axial displacement of the pressing element in addition to the effects achieved by the invention of claim 1, 2, 3 or 4 respectively, since all the cutouts of the pressing element are situated evenly in the circumferential direction.